1. Field of the Invention
The present invention relates generally to a micro adhesive nozzle for applying adhesive on a printed circuit board and an adhesive applying apparatus implementing such a nozzle. The present invention particularly relates to an adhesive nozzle that is capable of realizing stable application of adhesive for attaching micro components such as chip components, and preventing the occurrence of variations in the amount of adhesive being applied, the adhesive applying nozzle further being arranged so that a nozzle tip does not come into contact with the adhesive even when the space between the mounted chip components is narrow.
2. Description of the Related Art
Conventionally, in soldering chip components and insert components on a printed circuit board, a mass soldering process is conducted in a flow soldering bath. In conducting the soldering process, the chip components are provisionally attached to the printed circuit board using adhesive in order to prevent the mounted chip components from being detached even when the chip components are positioned at a bottom side of the printed circuit board.
As an exemplary method of provisionally attaching a chip component, an adhesive applying apparatus may be used to apply a suitable amount of adhesive at one or two points in between pads provided on the printed circuit board. Then, a chip component mounting apparatus may be used to mount the chip component after adjusting the positioning of the pads on the printed circuit board and the chip component electrode. Then, a mass heating process may be conducted using a hardening furnace, for example, to harden the applied adhesive and realize provisional attachment of the chip component.
In realizing the provisional attachment of chip components as is described above, an adhesive applying nozzle may be used to apply the adhesive as a micro-pattern. It is noted that exemplary applications of such a technique are described in Japanese Utility Model No. 2544122 and Japanese Patent No. 3498440.
Japanese Utility Model No. 2544122 discloses a technique of providing a pair of adhesive applying nozzle units and a pair of stopper units at a tip portion of a nozzle main body. However, according to this technique, the amount of adhesive being applied may not be sufficiently and stably controlled. Also, the nozzle may not be adaptable to different pad configurations for different types of chip components, and the space between the stopper units has to be taken into account in setting the space between the pads so that high-density component placement may be restricted.
Japanese Patent No. 3498440 discloses a technique of integrally forming a nozzle unit and a stopper unit to realize high-density mounting of micro components. However, according to this technique, the diameter of the applied adhesive may broaden beyond the allowed range, or adhesive may not be applied between a pair of nozzles.
It is noted that in recent years and continuing, miniaturization and price reduction of chip components is progressing as well as higher densification of electronic components (high-density component placement). In turn, techniques are demanded for accurately and stably supplying a suitable amount of adhesive for provisionally attaching small size chip components (micro chip components) without inducing the applied adhesive to spread to an electrode portion. However, problems exist in the prior art for suitably attaching small size chip components in such a manner, particularly with respect to 1005 size (i.e., 1.0×0.5 mm) chip components and smaller chip components. Thereby, in the prior art, small size chip components (micro chip components) of a 1005 size format or smaller may not be used in a printed circuit board that is subject to a mass soldering in a flow solder bath. Due to such a constraint, the design flexibility with respect to the placement of electronic components on the printed circuit board is limited.
In this regard, the present inventor has previously proposed a technique for enabling stable application of adhesive with little variations in the amount of adhesive being applied and narrowing of the spacing between adjacent chip components upon applying adhesive as a micro-pattern for attaching micro chip components on a printed circuit board, the technique involving providing a trench structure at a tip portion of a nozzle unit of an adhesive applying nozzle that applies adhesive on a printed circuit board.
However, according to the above proposed technique, when the space between adjacent chip components is narrow, the applied adhesive may come into contact with an adjacent chip component, and the applied adhesive may also come into contact with the tip of the nozzle so that the nozzle may have to be cleaned afterwards.